Method of purifying alkaline cyanids.



' fids and also, if desired, the alkaline carbon- UNITED STATES PAT NTOFFICE GEORGE CRAIG, OF GLASGOIV, SCOTLAND.

METHOD OF PURIFYING ALKALINE CYANIDIS.

SBEcIFIcA'rION forming part of Letters Patent No. 654,9;4, dated October22, 190i.

Application filed July 15, 1901. Serial No. 68,409. (No specimens.) 7

' T0 at whom it ma concern:

Be it known that I, GEORGE CRAIG, chemist, a subject of the King ofGreat Britain and Ireland, residing at 9 Hampden Terrace, in the city ofGlasgow, Scotland, have invented certain new and useful Improvements inor Connected with the Production orPu'rification of Alkaline Cyanids andI do hereby declare the following to be a full, clear, and exactdescription of the invention, such as will enable others skilled in theart to which it appertains to make and use the same.

The object of this invention is to effect the separation of alkalinesulfids and also, if desired, of alkaline carbonates from alkalinecyanids in the manufacture or purification of alkaline cyanids -forexample, in the production of alkaline cyanids from crude materialscontaining cyanogen-by treatment with liquefied ammonia, if suchmaterials have not been subjected to a preliminary treatment which willon subsequent extraction with liquefied ammonia produce cyanid free fromsuch impurity, or if such preliminarilytreated material has become dampand soluble sulfid has formed, or if from other causes the ammoniacalextracts therefrom are found to be contaminated with sulfids or withsulfids and carbonates.v According to this invention the alkaline cyanidsolution contaminated with such impurities is treated with an agent orwith agents which by double decomposition will separate the alkalinesulates therefrom. The agent or agents for offecting the separation mustbe insoluble or practically insoluble in the menstruum and formcompounds with the sulfur which are insoluble in the ammoniacal solutionand react with the carbonates, if it be desired to deal with these also.Suitable agents are the precipitated oxid of lead, the insoluble chloridof lead, the cyanids, chlorocyanids, oxycyanids, oxychlorids, and doublecyanids of lead, zinc, and cadmium, and cyanids of iron, or mixtures ofthese, or double compounds thereof. Ohlorids or cyanids of bariumstrontium or calcium will act to separate-carbonates, but will notseparate the sulfids completely.

The purifying operation can be carried out in air-tight vessels chargedwith the agent or agents selected and fitted with filtering ap pliancesand with means for passing the solution tlierethrough. Chlorid of leadcan;

for instance, be used as the said agent for removing; both sulfids andcarbonates. Chlorid of lead with ammonia forms (with increase of bulk)an insoluble compound which presents a very large surface and may bemixed with inert matter, if desirable, to increase its porosity. Thecyanids of lead do not form bulky compounds with ammonia, but reactinstantly with su'lfid, removing it completely.

The ammoniacal solution of impure cyanids is by passing through thepurifier or filter charged with chlorid of lead or with one or more ofthe other agents hereinbefore indicated, completely freed from sulfidsor from sulfids and carbonates, and on subsequent evaporation yields analkaline cyanid free from sulfur. and from carbonates, also if theagents be selected to react also with the carbonates, as is the casewith chlorid of lead.

When the purifying material is saturated with sulfids or sulfids andcarbonates, a freshly-charged purifier may be put into action and thefoul charge from the previous what manner the same is to be performed, I

declare that what I claim is- 1. The separation by double decompositionof alkaline sulfids, and carbonates, from ammoniacal solutions ofalkaline cyanids, by subjecting them to the action of an agent,insoluble in the menstruum and capable of forming compounds with thesulfur, which compounds are insoluble in the ammoniacal solution, and ofreacting with the carbonates, substantially as hereinbefore described.

2. The separation by double decomposition of alkaline sullids fromammoniacal solutions of alkaline cyanids by subjecting them to theaction of an agent insoluble in the menstruum and capable of forming,with the sulfur, compounds which are insoluble in the ammoniacalsolution, substantially as hereinbefore described.

of chlorid of lead, substantially as described.

4. The process of purifying ammoniacal solutions of alkaline cyanids bypassing the same through a specified lead salt insoluble in themenstruum, and forming, With the sulfur, compounds insoluble in theammoniacal solution, washing out the fouled agent With liquefiedammonia, expelling and recovering the ammonia, and reconverting theagent, as set forth. In testimony whereof I affix my signature inpresence of two witnesses.

GEORGE CRAIG. Vitnesses:

WM. 0. RUssELL, CHAS W. SMITH.

